The invention relates to image uniformity and compatibility, and more particularly, to image uniformity and compatibility by the use of digital darkness control or pixel stretch techniques in electronic imaging devices regardless of differences in development systems.
Resolution conversion is well known in the prior art. For example, Sharp U.S. Pat. No. 3,573,789 shows a resolution conversion technique by shifting each pixel with surrounding pixels into a resolution expander that automatically produces a multiple number of pixels corresponding to the center pixel. Image enhancement techniques to improve the quality of the image are also well known. For example, Coviello U.S. Pat. No. 4,450,483 statistically analyses a pixel with its surrounding pixels to make a determination whether or not the center pixel should remain as a black or white pixel or be changed to either a black or white pixel to improve the quality of the overall image. Walsh U.S. Pat. No. 4,437,122 does image enhancement of a digital image by taking each pixel of the digital image and a neighborhood surrounding the pixel and comparing this pattern to a set of reference patterns. Depending upon the match between the pixel and its neighborhood with a particular pattern, the center pixel is expanded into a plurality of predetermined pixels enhancing the overall quality of the image.
An ongoing difficulty in the art of recreating and reproducing images on a medium is the desirability of recreating the original image as close as possible regardless of the particular system used in recreating the image. In other words, it is important to match the images or have the images look alike regardless of the particular system in a given machine that is used in developing the image. Because of variances in development systems such as magnetic brush development, cascade development, and liquid development, the reproduced image will necessarily take on different characteristics in the reproduction of portions of the image in such characteristics as line width and solid area development. In addition, within a particular development system itself, the reproduction of a likeness of an original can be further altered by settings such as various degrees of copy quality such as normal, copy light, or copy dark. It is also a challenge in the prior art with multiple font types to be able to closely approximate electronically stored fonts in the reproduced image or text. This often involves painstaking trial and error of electronic representations of fonts and the analysis of the reproduced image. This process is, of course, further complicated, as mentioned above by different development processes that effect the reproduced image.
It would therefore be desirable to provide an electronic adjustment to an original image in order to compensate for various development systems in the prior art as well as to compensate for quality settings within a given development system. It would also be desirable to compensate for the use of different fonts and to be able-to match fonts within a reproduction system regardless of the font used and also taking into account the degrees of difference in development systems. It would also be desirable to compensate for variations in prior art systems by the use of an electronic adjustment to an original image that is two dimensional, that is, it can be made in the direction of a scanning beam or in the direction of movement of a medium in relation to the beam.
It is an object of the present invention, therefore, to provide a new an improved technique for improving reproduced images regardless of the development system and regardless of the font. It is another object of the present invention to improve the line delineation of reproduced images by adding pixels or partial pixels in both the X and Y- direction regardless of development characteristics. It is still another object of the present invention to be able to change the size of partial pixels in recreating an image in order to compensate for degrees of settings of the development system. Other advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.